The present invention relates to an efficient method for the preparation of ethylbenzene from toluene and methyl alcohol.
As is well known, the conventional way for the synthetic preparation of ethylbenezene is the addition reaction between ethylene and benezene. Along with the recent trend for the substitution of so-called C.sub.1 compounds, such as carbon monoxide, formaldehyde, methyl alcohol and the like, obtained from coals and other relatively cheap carbon sources for the starting materials derived from petroleums in the synthetic preparation of various kinds of petrochemicals in compliance with the increasing price of petroleums, however, efforts are directed more and more intensively to the conversion of the conventional process for the preparation of ethylbenzene into an alternative process utilizing inexpensive methyl alcohol and toluene in surplus supply as the starting materials. This method was first reported in 1967 by Yu. N. Sidorenko using a catalyst of zeolite 13X ion-exchanged with the ions of potassium, rubidium, cesium and the like.
The above mentioned method using zeolites as the catalyst carrier is, however, not satisfactory from the industrial standpoint because of the rapid decrease of the catalyst activity due to the susceptibility of the catalyst to coking through exhibiting high activity at the initial stage.
An alternative method has been recently proposed by use of activated carbon supporting potassium in place of zeolites (see, for example, Japanese Patent Kokai 52-133932) but the problem of coking remains unsolved even with the catalyst of this type.
The inventor has conducted extensive investigations with an object to overcome the problems in the conventional methods for the preparation of ethylbenezene from methyl alcohol and toluene and, as a result, has arrived at a discovery that addition of zinc and copper to a potassium-bearing catalyst of activated carbon is very effective in preventing coking with a remarkably improved yield of the ethylbenzene product, the effectiveness being specific to zinc and copper among metal species tested. The present invention has been completed on the basis of this discovery.